"Building a label printer using Python, Arduino, duct tape and paperclips" by Johan Beyers

A Lightning Talk at PyCon ZA 2020

Transcript

1. Building a label printer using Python, Arduino,
   duct tape and paperclips.
   And:
   ● Hot glue
   ● Cable ties
   ● A washing peg
   ● A ruler
   ● A hobby servo
   ● Skateboard bearings
   ● Polymorph (the plastic, not the company)
   ● Sandpaper
   ● A pencil
   ● A Coke can
   ● A series of tubes
   ● Plus various cannibalised bits from my garage
   

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2. Hackathon
   ● Half a weekend
   ● Build something useful
   ● Or not
   ● One step at a time
   ● TLAR design methodology
   I had an idea….
   

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3. The physical build
   Masking tape roll on a threaded rod, turning
   slowly.
   One rotation moves it 1mm sideways (spiral).
   Detect a starting point (Coke can, paperclips).
   Raise/lower a pen to create pixels.
   

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4. Software
   Laptop running a Python script:
   ● Convert text to image
   ● Convert image to list of lists of colour
   values
   ● Send timed up/down commands to Arduino
   Arduino is just a dumb controller:
   ● Drive the motor
   ● Send a start position trigger to the laptop
   ● Receive up/down and move the pen
   

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5. Python: Getting the image
   

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6. Python: Control
   

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7. Results:
   ● 11 hours zero to Hello World
   ● 48 lines of Python code
   ● 68 lines of Arduino code
   ● 0 test coverage
   ● 40 labels printed to date
   ● 8 minutes per label
   ● 1 lightning talk
   Definitely worth it, would do
   again.
   

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8. http:/
   /johan.beyers.co.za
   Talk to me about:
   ● Python
   ● Takealot (We’re hiring!)
   ● Maker evenings (on hold)
   Or some other projects:
   ● 3D printer
   ● Dog speedometer
   ● Simple drawing machine
   ● Perpetual Pendulum Wave
   ● Electric bicycle
   

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